The first objective of this proposal is to identify the mechanism of action of delta9-tetrahydrocannabinol (THC), thought to be the principal psychoactive component of marihuana, and other drugs (e.g., alcohol, pentobarbital) on behavioral processes in sequences of offensive-dominant and defensive-submissive postures and movements in fighting episodes in rats. Drug effects will be studied on several behavioral components characteristic of dominance and submission when either one or both opponents are injected, acutely or chronically. A second objective is to assess the effects of THC and other drugs on several automatically monitored behaviors, including aggressive and non-aggressive actions. In comparable experimental paradigms the aggressive biting and operant performance of rats and monkeys in reaction to omission of reinforcement are automatically recorded. These procedures permit reliable, objective and accurate measurements of the drugs, selective action on aggressive behavior, comparing two species tested under closely similar conditions. The third objective is to determine changes in the dynamics of brain amine metabolism that are produced by (1) THC and other drugs, (2) engagement in offensive-dominant or defensive-submissive behaviors, and (3) drug-induced changes in aggressive behavior.